List blendfile.py fields for RenderData
The data structure seems to be python dictionaries pointing to addresses in memory.
Given your above code you can see the dictionaries by using

DNA_struct_of_scene = scene.file.structs[scene.sdna_index]
rel_dict = DNA_struct_of_scene.field_from_name[b'r'].dna_type.field_from_name


From the dict posted below, you can use 

scene[b"r",b'size']


to get the render scale and

scene[b'r',b'frs_sec']


to get the frames per second

rel dict = 
 {b'im_format': &lt;__main__.DNAField at 0x7f4e476aa990&gt;,
 b'avicodecdata': &lt;__main__.DNAField at 0x7f4e476aa9d8&gt;,
 b'qtcodecdata': &lt;__main__.DNAField at 0x7f4e476aaa20&gt;,
 b'qtcodecsettings': &lt;__main__.DNAField at 0x7f4e476aaa68&gt;,
 b'ffcodecdata': &lt;__main__.DNAField at 0x7f4e476aaab0&gt;,
 b'cfra': &lt;__main__.DNAField at 0x7f4e476aaaf8&gt;,
 b'sfra': &lt;__main__.DNAField at 0x7f4e476aab40&gt;,
 b'efra': &lt;__main__.DNAField at 0x7f4e476aab88&gt;,
 b'subframe': &lt;__main__.DNAField at 0x7f4e476aabd0&gt;,
 b'psfra': &lt;__main__.DNAField at 0x7f4e476aac18&gt;,
 b'pefra': &lt;__main__.DNAField at 0x7f4e476aac60&gt;,
 b'images': &lt;__main__.DNAField at 0x7f4e476aaca8&gt;,
 b'framapto': &lt;__main__.DNAField at 0x7f4e476aacf0&gt;,
 b'flag': &lt;__main__.DNAField at 0x7f4e476aad38&gt;,
 b'threads': &lt;__main__.DNAField at 0x7f4e476aad80&gt;,
 b'framelen': &lt;__main__.DNAField at 0x7f4e476aadc8&gt;,
 b'blurfac': &lt;__main__.DNAField at 0x7f4e476aae10&gt;,
 b'edgeR': &lt;__main__.DNAField at 0x7f4e476aae58&gt;,
 b'edgeG': &lt;__main__.DNAField at 0x7f4e476aaea0&gt;,
 b'edgeB': &lt;__main__.DNAField at 0x7f4e476aaee8&gt;,
 b'fullscreen': &lt;__main__.DNAField at 0x7f4e476aaf30&gt;,
 b'xplay': &lt;__main__.DNAField at 0x7f4e476aaf78&gt;,
 b'yplay': &lt;__main__.DNAField at 0x7f4e476aafc0&gt;,
 b'freqplay': &lt;__main__.DNAField at 0x7f4e476ab048&gt;,
 b'depth': &lt;__main__.DNAField at 0x7f4e476ab090&gt;,
 b'attrib': &lt;__main__.DNAField at 0x7f4e476ab0d8&gt;,
 b'frame_step': &lt;__main__.DNAField at 0x7f4e476ab120&gt;,
 b'stereomode': &lt;__main__.DNAField at 0x7f4e476ab168&gt;,
 b'dimensionspreset': &lt;__main__.DNAField at 0x7f4e476ab1b0&gt;,
 b'filtertype': &lt;__main__.DNAField at 0x7f4e476ab1f8&gt;,
 b'size': &lt;__main__.DNAField at 0x7f4e476ab240&gt;,
 b'maximsize': &lt;__main__.DNAField at 0x7f4e476ab288&gt;,
 b'pad6': &lt;__main__.DNAField at 0x7f4e476ab2d0&gt;,
 b'xsch': &lt;__main__.DNAField at 0x7f4e476ab318&gt;,
 b'ysch': &lt;__main__.DNAField at 0x7f4e476ab360&gt;,
 b'xparts': &lt;__main__.DNAField at 0x7f4e476ab3a8&gt;,
 b'yparts': &lt;__main__.DNAField at 0x7f4e476ab3f0&gt;,
 b'tilex': &lt;__main__.DNAField at 0x7f4e476ab438&gt;,
 b'tiley': &lt;__main__.DNAField at 0x7f4e476ab480&gt;,
 b'planes': &lt;__main__.DNAField at 0x7f4e476ab4c8&gt;,
 b'imtype': &lt;__main__.DNAField at 0x7f4e476ab510&gt;,
 b'subimtype': &lt;__main__.DNAField at 0x7f4e476ab558&gt;,
 b'quality': &lt;__main__.DNAField at 0x7f4e476ab5a0&gt;,
 b'displaymode': &lt;__main__.DNAField at 0x7f4e476ab5e8&gt;,
 b'use_lock_interface': &lt;__main__.DNAField at 0x7f4e476ab630&gt;,
 b'pad7': &lt;__main__.DNAField at 0x7f4e476ab678&gt;,
 b'scemode': &lt;__main__.DNAField at 0x7f4e476ab6c0&gt;,
 b'mode': &lt;__main__.DNAField at 0x7f4e476ab708&gt;,
 b'raytrace_options': &lt;__main__.DNAField at 0x7f4e476ab750&gt;,
 b'raytrace_structure': &lt;__main__.DNAField at 0x7f4e476ab798&gt;,
 b'pad1': &lt;__main__.DNAField at 0x7f4e476ab7e0&gt;,
 b'ocres': &lt;__main__.DNAField at 0x7f4e476ab828&gt;,
 b'pad4': &lt;__main__.DNAField at 0x7f4e476ab870&gt;,
 b'alphamode': &lt;__main__.DNAField at 0x7f4e476ab8b8&gt;,
 b'osa': &lt;__main__.DNAField at 0x7f4e476ab900&gt;,
 b'frs_sec': &lt;__main__.DNAField at 0x7f4e476ab948&gt;,
 b'edgeint': &lt;__main__.DNAField at 0x7f4e476ab990&gt;,
 b'safety': &lt;__main__.DNAField at 0x7f4e476ab9d8&gt;,
 b'border': &lt;__main__.DNAField at 0x7f4e476aba20&gt;,
 b'disprect': &lt;__main__.DNAField at 0x7f4e476aba68&gt;,
 b'layers': &lt;__main__.DNAField at 0x7f4e476abab0&gt;,
 b'actlay': &lt;__main__.DNAField at 0x7f4e476abaf8&gt;,
 b'mblur_samples': &lt;__main__.DNAField at 0x7f4e476abb40&gt;,
 b'xasp': &lt;__main__.DNAField at 0x7f4e476abb88&gt;,
 b'yasp': &lt;__main__.DNAField at 0x7f4e476abbd0&gt;,
 b'frs_sec_base': &lt;__main__.DNAField at 0x7f4e476abc18&gt;,
 b'gauss': &lt;__main__.DNAField at 0x7f4e476abc60&gt;,
 b'color_mgt_flag': &lt;__main__.DNAField at 0x7f4e476abca8&gt;,
 b'postgamma': &lt;__main__.DNAField at 0x7f4e476abcf0&gt;,
 b'posthue': &lt;__main__.DNAField at 0x7f4e476abd38&gt;,
 b'postsat': &lt;__main__.DNAField at 0x7f4e476abd80&gt;,
 b'dither_intensity': &lt;__main__.DNAField at 0x7f4e476abdc8&gt;,
 b'bake_osa': &lt;__main__.DNAField at 0x7f4e476abe10&gt;,
 b'bake_filter': &lt;__main__.DNAField at 0x7f4e476abe58&gt;,
 b'bake_mode': &lt;__main__.DNAField at 0x7f4e476abea0&gt;,
 b'bake_flag': &lt;__main__.DNAField at 0x7f4e476abee8&gt;,
 b'bake_normal_space': &lt;__main__.DNAField at 0x7f4e476abf30&gt;,
 b'bake_quad_split': &lt;__main__.DNAField at 0x7f4e476abf78&gt;,
 b'bake_maxdist': &lt;__main__.DNAField at 0x7f4e476abfc0&gt;,
 b'bake_biasdist': &lt;__main__.DNAField at 0x7f4e476ad048&gt;,
 b'bake_samples': &lt;__main__.DNAField at 0x7f4e476ad090&gt;,
 b'bake_pad': &lt;__main__.DNAField at 0x7f4e476ad0d8&gt;,
 b'bake_user_scale': &lt;__main__.DNAField at 0x7f4e476ad120&gt;,
 b'bake_pad1': &lt;__main__.DNAField at 0x7f4e476ad168&gt;,
 b'pic': &lt;__main__.DNAField at 0x7f4e476ad1b0&gt;,
 b'stamp': &lt;__main__.DNAField at 0x7f4e476ad1f8&gt;,
 b'stamp_font_id': &lt;__main__.DNAField at 0x7f4e476ad240&gt;,
 b'pad3': &lt;__main__.DNAField at 0x7f4e476ad288&gt;,
 b'stamp_udata': &lt;__main__.DNAField at 0x7f4e476ad2d0&gt;,
 b'fg_stamp': &lt;__main__.DNAField at 0x7f4e476ad318&gt;,
 b'bg_stamp': &lt;__main__.DNAField at 0x7f4e476ad360&gt;,
 b'seq_prev_type': &lt;__main__.DNAField at 0x7f4e476ad3a8&gt;,
 b'seq_rend_type': &lt;__main__.DNAField at 0x7f4e476ad3f0&gt;,
 b'seq_flag': &lt;__main__.DNAField at 0x7f4e476ad438&gt;,
 b'pad5': &lt;__main__.DNAField at 0x7f4e476ad480&gt;,
 b'simplify_flag': &lt;__main__.DNAField at 0x7f4e476ad4c8&gt;,
 b'simplify_subsurf': &lt;__main__.DNAField at 0x7f4e476ad510&gt;,
 b'simplify_subsurf_render': &lt;__main__.DNAField at 0x7f4e476ad558&gt;,
 b'simplify_shadowsamples': &lt;__main__.DNAField at 0x7f4e476ad5a0&gt;,
 b'pad9': &lt;__main__.DNAField at 0x7f4e476ad5e8&gt;,
 b'simplify_particles': &lt;__main__.DNAField at 0x7f4e476ad630&gt;,
 b'simplify_particles_render': &lt;__main__.DNAField at 0x7f4e476ad678&gt;,
 b'simplify_aosss': &lt;__main__.DNAField at 0x7f4e476ad6c0&gt;,
 b'cineonwhite': &lt;__main__.DNAField at 0x7f4e476ad708&gt;,
 b'cineonblack': &lt;__main__.DNAField at 0x7f4e476ad750&gt;,
 b'cineongamma': &lt;__main__.DNAField at 0x7f4e476ad798&gt;,
 b'jp2_preset': &lt;__main__.DNAField at 0x7f4e476ad7e0&gt;,
 b'jp2_depth': &lt;__main__.DNAField at 0x7f4e476ad828&gt;,
 b'rpad3': &lt;__main__.DNAField at 0x7f4e476ad870&gt;,
 b'domeres': &lt;__main__.DNAField at 0x7f4e476ad8b8&gt;,
 b'domemode': &lt;__main__.DNAField at 0x7f4e476ad900&gt;,
 b'domeangle': &lt;__main__.DNAField at 0x7f4e476ad948&gt;,
 b'dometilt': &lt;__main__.DNAField at 0x7f4e476ad990&gt;,
 b'domeresbuf': &lt;__main__.DNAField at 0x7f4e476ad9d8&gt;,
 b'pad2': &lt;__main__.DNAField at 0x7f4e476ada20&gt;,
 b'dometext': &lt;__main__.DNAField at 0x7f4e476ada68&gt;,
 b'line_thickness_mode': &lt;__main__.DNAField at 0x7f4e476adab0&gt;,
 b'unit_line_thickness': &lt;__main__.DNAField at 0x7f4e476adaf8&gt;,
 b'engine': &lt;__main__.DNAField at 0x7f4e476adb40&gt;,
 b'bake': &lt;__main__.DNAField at 0x7f4e476adb88&gt;,
 b'preview_start_resolution': &lt;__main__.DNAField at 0x7f4e476adbd0&gt;,
 b'debug_pass_type': &lt;__main__.DNAField at 0x7f4e476adc18&gt;,
 b'pad': &lt;__main__.DNAField at 0x7f4e476adc60&gt;,
 b'views': &lt;__main__.DNAField at 0x7f4e476adca8&gt;,
 b'actview': &lt;__main__.DNAField at 0x7f4e476adcf0&gt;,
 b'views_format': &lt;__main__.DNAField at 0x7f4e476add38&gt;,
 b'pad8': &lt;__main__.DNAField at 0x7f4e476add80&gt;,
 b'mblur_shutter_curve': &lt;__main__.DNAField at 0x7f4e476addc8&gt;}